The present invention relates to separable electrical connector assemblies, and more particularly to such a connector assembly having a modified dwell position.
Separable connector assemblies for underground power distribution cable, or shielded cable, are watertight when assembled and may be readily separated into two or more units to break a cable connection. Such units are separately commercially available and are commonly referred to as "modules". A connector assembly includes two or more matching modules assembled together. In accordance with customer requirements, standardization of the dimensions of parts allows for interchangeability of correspondingly rated modules of different manufacturers.
One type of separable connector assembly commonly used is a "rod and bore" switching type. In this assembly, a switch module includes a receiving bore tube, or snuffer, which is situated within a passageway in a shielded, insulating housing. The passageway includes a grasping contact member at the interior end of the bore tube. A matching rod connector module includes a rod contact member which is inserted into the bore tube for electrical engagement with the bore grasping contact member. Exemplary rod and bore type separable electrical connector assemblies are disclosed in the following U.S. Pat. Nos.: 3,542,986 issued Nov. 24, 1970 to Kotski; 3,551,587 issued Dec. 29, 1970 to Propst; and 3,587,035 issued June 22, 1970 to Kotski.
Generally, in the previously described connector assemblies, means for extinguishing arcs generated in breaking electrical contact are provided. A common technique is to provide the bore of the snuffer tube with a liner of ablative material, i.e., a material which generates arc extinguishing gases when subjected to an electric arc. In addition, the rod contact member includes an arc follower, a rod shaped extension at the end of the rod contact. The arc follower is also of ablative material. Thus, when the rod contact is pulled from the grasping contact of the bore module, i.e., "loadbreak" conditions, the resulting arc passes between the arc follower and the snuffer liner thereby exposing the ablative material to the arc. The ablative material then generates arc extinguishing gases which rapidly extinguish the arc. This permits the connector assembly to be utilized as a switch which is operable under energized conditions.
Although the previously described separable electrical connector assemblies are widely used, they do suffer from certain problems. To fully appreciate such problems, it is necessary to review the industrial practices common to separable electrical connector assembly usage. More particularly, in connection with making electrical contact between the rod and bore contacts, or "loadmake" condition, an operator manually moves the rod connector module (with its rod contact member) toward engagement with the bore grasping contact member of the switch module through the use of a conventional "hot stick" or other suitable insulating means. The point at which a noticeable resistance to further insertion of the rod contact member into the switch module is felt is generally defined as the "dwell position" of the connector assembly. The dwell position is associated with the position in which the arc follower of the rod contact member first engages the bore grasping contact. At this point, only the length of the arc follower separates the conductive rod contact and the bore grasping contact. Operators are cautioned not to hold the rod contact member in this dwell position but to instead immediately thrust the rod contact member further into the switch module to electrically engage the rod contact member with the bore grasping contact.
It is to be further appreciated that certain standards have been established for testing separable electrical connector systems which are designed for making and breaking electrical contact, i.e., loadmake and loadbreak operation. For example, ANSI Standards (C119.2) of Revision 1 include the following operating procedure: "The operator shall maintain a minimum dwell time of 5 seconds after the probe (arc follower of the rod contact member) is positioned in the arc extinguishing area of its mating part (switch module)". This is generally interpreted as the dwell position.
Tests have shown that the dwell position previously referred to is satisfactory at contact voltages between rod and bore up to about 22 kV in standard electrical connector assemblies such as those having a 8.3/14.4 kV three phase rating or a 21.2 kV single phase rating. However, at the next higher standard contact voltage of 26.3 kV, electrical breakdown may occur across the arc follower, even when operating in accordance with standard minimum dwell time conditions. This results in an undesirable prestrike which is detrimental to successful operation of the connector assembly. Although the undesirable prestrike condition can be prevented through several techniques, none of the available techniques is satisfactory. One such technique is to make the arc follower sufficiently long so as to withstand the increased contact voltage. This technique thus requires an increased length of the switch module which interferes with the presently existing need for interchangeability of connector assembly parts. Other techniques have included the use of an acceptable standard length of arc follower, e.g., 2.3 to 2.5 inches in combination with conductive core pins in the arc follower. However, this technique has not shown the ability to consistently withstand a contact voltage of 26.3 kV.
Therefore, it is a general object of this invention to provide an improved separable electrical connector assembly in which there is reduced chance for an intercontact breakdown when the connector module is in the dwell position.
Another object of this invention is to provide such a separable electrical connector assembly which can be operated in a manner consistent with common industrial usage.
Another object of this invention is to provide such a separable electrical connector assembly in which a modified dwell position is provided.
Another object of this invention is to provide such a separable electrical connector assembly in which the modified dwell position minimizes the need to depart from conventional electrical connector structure.
Another object of this invention is to provide such a separable electrical connector assembly which is capable of operation at 26.3 kV or higher.
Another object of the present invention is to provide an increased voltage rating for a connector assembly having a given arc follower.
Further objects and advantages will become apparent as the description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of the specification.